Japanese knotweed – do's and don'ts

The presence of Japanese knotweed on a construction site may be unwelcome and an unpleasant surprise, however it can often be dealt with in a reliable and cost effective manner.


  • (If you have time) start an herbicide control programme. Virtually all knotweed solutions rely on herbicide applications being done before other remediation works can be undertaken. As herbicide programmes can only effectively be undertaken in the growing season, this is often limited to a period between May and October - sometimes less if we have a cold spring or early frosts in autumn.
  • Commission an expert site survey, looking specifically for invasive weeds.
  • Fence off the knotweed before beginning any earth-moving works on site.
  • Commission a Knotweed Management Plan.
  • Read the Environment Agency's Code of Practice – 'Managing Japanese knotweed on development sites'.
  • Contact The Knotweed Company on 01327 340770 or email brian@jkweed.co.uk for bespoke solutions and free quotations on possible solutions


  • Allow demolition workers or ground workers to commence works without securing the knotweed areas.
  • Allow Knotweed contaminated material to leave site unintentionally. Knotweed contaminated materials are classed as controlled waste and if leaving site, must be disposed of properly at a licensed landfill site.
  • Allow Japanese knotweed to establish and spread off site. This may be an offence under the Wildlife and Countryside Act and even involve you in litigation with your neighbours.
  • Flail or strim green knotweed stems. This is one of the surest ways of spreading viable pieces of knotweed over a much larger area - making the problem far worse.
  • Compost knotweed material, it won't kill it.
  • Commission solutions that aren't supported by the Environment Agency's Code of Practice or the Herbicide Manufacturers.